Trickling filter



Dec. 3, 1963 K. I .scHULzE TRIcxLING FILTER Filed July 15, 1960 BY w United States Patent() 3,113,1ll2 'ERESKLING FILTER Karl Ludwig Settala MS Spmftan Ave., East Lansing, Mich. Filed .iuly i5, 19nd, Ser. No. 4.3,ll3 2 Claims. (El. 2id-lh) The present invention relates to trickling filters and more particularly to a self supporting modular open-work lilter for use in sewage treatment plants and the like. Still more particularly the present invention relates to large mesh screen panels joined in such a manner as to be tree standing and load supporting while being light in weight and exposing a maximum surface for biological activity and remaining non-clogging.

Conventional trickling filters are beds of crushed rock over and through which Water to be freed of bacterial oxygen demand or polluting matter is passed. The rock provides a support for growth of a bacterial film in relationship to its area. The diiiiculty with such iilters is that the voids between rocks quickly become plugged or clogged and the eiiiciency of the filter accordingly drops. In place of the crush rock specially prepared vertically oriented tile or cermaic pieces have been arranged in geometric patterns in attempted avoidance ot clogging and the like.

Such devices are known in the patent art as represented by Schulhotl in United States Letters Patent 2,188,162. To my knowledge none have gone materially beyond the ceramic teachings of Schulhoii and none have proposed a trickling lter wherein the lter media is simple open mesh screening.

Trickling filters must provide a base media for the growth and maintenance of slimes in which aerobic bac teria may operate upon the aqueous waste passing over the slime surface. The aerobic bacteria must be under aerobic conditions at the water film-slime interphase by a supply of dissolved oxygen from oxygen containing gas such as air and passing through the water nlm. The present invention, as will be seen, provides a very satisfactory support media and in addition provides an open void work which is completely non-clogging therefore assuring continuous interphase between aqueous organic waste material and air. As will be seen the etliciency of the present filter exceeds that ot prior known trickling filters.

Accordingly one of the objects ot the present invention is to provide a trickling filter media containing about 99.3 percent voids and wherein the voids are substantially nonclogging.

Another object is to provide a filter media of light weight and high strength against vertical loading or stacking.

Other objects include the development of simple stackable tilter media cartridges amenable to modular installation and having a hih capacity for example about l() to 80 million gallons per acre per day at eiciences of about 80 percent B.O.D. (bacterial oxygen demand) removal at the lower iiow and about 58 percent B.O.D. removal at the higher iiow without recycle. In standard type crushed rock trickling filters with hydraulic load at 4 million gallons per acre per day the efliciency ot 85 percent BOD. removal is considered excellent. Simplicity is an obvious objective as well as overall economy including minimum foundation support for the light weight units in tiered or stacked relationship.

Still other objects include the provision of a mesh or screen type media which avoids clogging and which provides an ideal surface for the growth of microbial slimes and coatings.

In the drawings:

FIGURE l is a perspective view of a trickling iilter Mice media in module form prepared in accord with the present invention.

FIGURE 2 is an elevation view of a single mesh of the hardware cloth comprising the structure from which the filter of FIGURE l is formed.

FGURE 3 is a plan view of the sinusoidally formed corrugations indicating how two formed elements are joined together.

FIGURE 4 is a schematic cross section taken through a single wire strand and indicating the support for the microbial mass.

FIGURE 5 is a perspective view or a plurality of trickling iilter units in stacked relationship for insertion in a sewage purification plant or water treatment plant.

FIGURE 6 is a plan View of a modified structure in accord with the present invention and showing a spiral arrangement of the trickling lilter structure,

DESCRIPTION Referring to the drawings, FIGURE 1 illustrates a single unit 11 of the trickling iilter of the present invention. The lter 11 comprises a plurality orp sheets 12 formed in vertical corrugations 13 and jointed together at the contact junctures 1d between adjacent and oppositely oriented sheets l2. luncture is accomplished by simple stapling, welding, or interweaving as is well known in the art. The material forming the sheets 12 is steel hardware cloth and which may be coated as by known galvanizing processes or the selection of corrosion resistant materials. In some instances the preparation of plastic or resin grids in sheet form may be satisfactory. As will be appreciated by reference to FIGURE 2, the hardware cloth should be provided with open-work mesh l5 so as to provide in excess of percent voids ld. The sheets l2 when formed into a l foot by 1 foot by 3 foot unit oi filter 1i should resist between 1200 and 1300 or better pounds per square foot under vertical loading. Very good results are obtained using 19 gauge hardware cloth in 1/2 inch mesh, galvanized.

As best illustrated in the plan view of FIGURE 3 sinusoidal corrugations i7 are prepared for providing a vertical pattern of hardware cloth most resistant to clogging by the avoidance of tight corners as may be found in zig-zag corrugation or other convolutions. This is not intended to restrict the invention to the specific sinusoidal form but simply indicates that the sinusoidal form is preerred over simple zig-zag corrugations in providing a minimum amount of entrapment areas or corners which may cause the mediato plug or clog.

With reference to FIGURE 4 the mechanism or" the trickling lter is best described. A single strand or wire 18 is illustrated and which may be considered as one of the vertical strands in the iilter ll. To either side and surrounding the wire lil is a biological film 19 which cumulates in use and provides the supporting bed for aerobic micro organisms. Liquid waste Ztl is tricltled continuously over the biological iilrn l@ so as to provide an interphase of liquid to organic culture. This microbial bed is an organic mass receiving organic waste material or pollutant for aerobic destruction. Equally important is the air to liquid interphase providing an exchange of carbon dioxide and oxygen. The carbon dioxide is the gaseous product of aerobic bacterial activity. i he oxygen is essential in maintaining the biological film in an aerobic condition. As will be appreciated as a consequence ot physical analysis of the open work structure, very little opportunity is provided for the development of anaerobic conditions. The clogging as between plural pieces of support media is substantially completely avoided.

As will be appreciated the smooth interphase between support media in the present invention and rock, for example, facilitates the sloughing oli of accumulated biological growth, usually prior to the development of anaerobic conditions at the media to iilin interphase. Further, by reason of the tubular vertical openings 24 as between adjacent convolutions as shown in FIGURE 3 sloughing is allowed to occur without interference troni the support surfaces and the openings 24 allow free passage of air during build up of microbial iilrn it?,

In FIGURE 5 a characteristic stacked or tiered arrangement is illustrated as would lbe utilized in a trickling iilter installation. The filter 2l is made up of a plurality of ilter units 11. The limits of horizontal extension are nfinite while the vertical stacking is a 'matter determined by the inherent rigidity and resistance to crusing built into the presently described unit with stability achieved by the corrugated tonni and vertical orientation. Of collateral economic importance the light weight of the present filters in tiered relationship avoids the necessity for foundation or support structures of great strength. When using the structure of FGURE 1 as described with 19 gauge stock the Weight is about 3 pounds per Icubic foot.

FGURE 6 shows a cylindrical niodilication of a lter media unit 22 while employing corrugations in la single sheet and Wound 23 in spiral orrn. This device has all of the structural features present in unit 11 and additionlly avoids the requirements of fastening. It will be appreciated that successive rings or -convolutions of the sheet comprising unit 22 are in spaced apart relation from each other.

ln performance iilter niedia structures in accord With the present invention provide 8 times the liovv capacity ot former rock illters. The advantages on a comparative basis can be appreciated by reference to the following Tables I 'and li.

The use of a screen form of filter media in accord with the present invention provides a continuous interrupted liov/ in delay of free flow as the waste laden aqueous material courses down the lattice-like form. This results in `an extended time contact period with the biological iilin 1while allowing transverse as well as vertical air passage through the voids.

Having thus described rny invention and specic enibodinients thereof various adaptations and rnodiiications of my invention will occur to those skilled in the art and 4 such modifications are intended to be included herein limited only by the scope of the hereinafter appended claims.

l claim:

1. ln a tricljing filter for supporting a biological culture in an aerobic process for destruction of organic materials dispersed in an aqueous liow and wherein the ilow is vertical form tcp to bottom, the combination comprising:

(o) a plural-ity of open work grid screens, the transverse openings theretirough each being in vertical plane relationship and said grid members defining said openings providing guide liow surfaces and said transverse openings thus defined, being substantially larger than any dispersed sol-ids in said aqueous iiow;

(b) adjacent of said grid screens being vertically corrugated to resist vertical axial stresses'in excess of the weight o1 said grid screens, biological growth thereon, and aqueous ow dov/n said surfaces, and adjacent peaks of said corrugations joined in vertical Contact seams thereby defining columnar vertical `voids of a size substantially in excess of the size or" any dispersed solids in said aqueous iiow; and

(c) a plurality of said grid screens thus fonmed grouped and secured in a unit illing a spatial volume and a plurality of said units being stacked so that all of said columnar voids in each of said units are in parallel vertical relation.

2. A modular tricliling filter structure providing a lightweight media for support or" biological yrowtll and wherein an aqueous intluent carrying dispersed organic material is introduced for downward triciding, the combination comprising:

(o) a plurality of open-Work grid screens wherein all transverse openings therethrough are in vertical plane relationship and said grid members defining said openings providing guide iow surfaces, and said transverse openings, thus delined, being substantially larger than `any dispersed solids in said aqueous llow, vand said grid screen being vertically corrugated to resist vertical axial stresses applied to said grid screen in excess of the Weight of said grid screen, biological growth thereon, and aqueous iiow down said surfaces;

(b) unit modules prepared by joining a plurality of said grid screens in adjacent parallel relationships along vertical contacting edges whereby ver-tical co1- umnar voids are presented;

(c) tand a stack of said unit modules, thus prepared, in vertical tie-red relationship in accord `with desired volume and tlow, said modules resisting crushing by reason of their corrugated form and adjacent joined relationship While providing grid media on which said biological growth can proceed.

References Cited in the tile of this patent UNITED STATES PATENTS 2,188,162 Schu'lholi` lan. 23, 1940 2,334,263 Hartwell Nov. 16, 1943 2,354,931 Tohnan Aug. 1, 1944 2,651,414 Lawson Sept. 8, 1953 FOREIGN PATENTS 534,385 Great Britain Mar. 5, 1941 770,202 Great Britain Mar. 20, 1957 

1. IN A TRICKLING FILTER, FOR SUPPORTING A BIOLOGICAL CULTURE IN AN AEROBIC PROCESS FOR DESTRUCTION OF ORGANIC MATERIALS DISPERSED IN AN AQUEOUS FLOW AND WHEREIN THE FLOW IS VERTICAL FORM TOP TO BOTTOM, THE COMBINATION COMPRISING: (A) A PLURALITY OF OPEN WORK AND GRID SCREENS, THE TRANSVERSE OPENINGS THERETHROUGH EACH BEING IN VERTICAL PLANE RELATIONSHIP AND SAID GRID MEMBERS DEFINING SAID OPENINGS PROVIDING GUIDE FLOW SURFACES AND SAID TRANSVERSE OPENINGS THUS DEFINED, BEING SUBSTANTIALLY LARGER THAN ANY DISPERSED SOLIDS, IN SAID AQUEOUS FLOW; (B) ADJACENT OF SAID GRID SCREENS BEING VERTICALLY CORRUGATED TO RESIST VERTICAL AXIAL STRESSES IN EXCESS OF THE WEIGHT OF SAID GRID SCREENS, BIOLOGICAL GROWTH THEREON, AND AQUEOUS FLOW DOWN SAID SURFACES, AND ADJACENT PEAKS AND SAID CORRUGATIONS BEING JOINED IN VERTICAL CONTACT SEAMS THEREBY DEFINING COLUMNAR VERTICAL VOIDS OF A SIZE SUBSTANTIALLY IN EXCESS OF THE SIZE OF ANY DISPERSED SOLIDS IN SAID AQUEOUS FLOW; AND (C) A PLURALITY OF SAID GRID SCREENS THUS FORMED GROUPED AND SECURED IN A UNIT FILLING A SPATIAL VOLUME AND A PLURALITY OF SAID UNITS BEING STACKED SO THAT ALL OF SAID COLUMAR VOIDS IN EACH OF SAID UNITS ARE IN PARALLEL VERTICAL RELATION. 